Autonomous machine

ABSTRACT

An electric machine, such as an autonomous vacuum cleaner, is powered through a cable and includes a means or device for detecting the orientation of the cable with respect to the main body of the machine that may be in the form of a pivotable member such as pendulum, connected to a potentiometer. The potentiometer provides an output signal proportional to the position of the free end of the pendulum. Thus, the machine can detect the position of the cable and thus can avoid it or else follow it. Microswitches may also be provided to detect extreme positions of the cable.

This invention relates to an autonomous machine powered by a power cable, for example a robotic vacuum cleaner.

There have been various proposals to provide autonomous or robotic machines for performing duties such as cleaning or polishing a floor area, or for mowing grass. Some autonomous machines are capable of exploring the environment in which they are placed without human supervision, and without advance knowledge (e.g. a map) of the layout of the environment. The machine may explore the environment during a learning phase and will subsequently use this information during a working phase, or the machine may begin working in the area immediately. Autonomous machines of this type are particularly attractive to users as they can be left to work with minimal human supervision.

It is also known to provide autonomous machines which derive their power from a mains power supply and which carry a reel of cable which is dispensed as the machine moves around the area. U.S. Pat. No. 4,962,453 shows an example of this kind of machine, which covers a working area by a complex series of fan-shaped coverage patterns.

A problem which may be encountered with cable-powered machines is that the cable itself can hamper the functioning of the machine. For example, if an autonomous machine runs over its own cable, it may experience odometry errors or may damage the cable.

The invention provides an autonomous machine comprising a main body, a power cable and means for detecting the orientation of the cable with respect to the main body

The invention permits the machine to detect the position of its own cable. The machine may therefore be controlled so as to avoid or to follow its own cable.

Preferably, the means for detecting cable orientation comprises a first detecting means arranged to detect the orientation of the cable within a first predetermined range. A second detecting means arranged to detect the orientation of the cable within a second predetermined range may also be provided. The first and second ranges may be separate or may overlap.

Advantageously, the first detecting means comprises a rotatable member connected to a rotary encoder such as a potentiometer. A suitable rotatable member is a pendulum, one end portion of which is connected to the cable, the other end portion of which is associated with the encoder.

The second detecting means may comprises one or more pressure switches, such as microswitches, arranged adjacent the cable, to produce a signal when the cable pushes against it. Alternatively, an intermediary member such as a collar around the cable may be arranged to push against the switches when the cable is deflected.

The machine can take many forms: it can be a floor treating machine such as a vacuum cleaner or floor polisher, a lawn mower or a robotic machine which performs some other function. Alternatively, it could be a general purpose robotic vehicle which is capable of carrying or towing a work implement chosen by a user.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:—

FIG. 1 is a perspective view of an autonomous machine in the form of a vacuum cleaner;

FIG. 2 shows the electrical systems of the machine of FIG. 1;

FIGS. 3A-3D (collectively “FIG. 3”) are perspective views showing a power cable management system of the machine of FIGS. 1 and 2 incorporating the present invention;

FIG. 4 is a flow chart of a navigation method used by the machine;

FIGS. 5 and 6 are plan views showing the machine at work in a working area, following the navigation method of FIG. 4;

FIGS. 7A, 713 and 7C (collectively “FIG. 7”) are plan views illustrating a movement carried out by the machine of FIG. 1 using the navigation method of FIG. 4;

FIGS. 8 and 9 are plan views illustrating ways in which the machine copes with large working areas;

FIGS. 10 a-10 d (collectively “FIG. 10”) are perspective views showing an alternative embodiment of the invention; and

FIGS. 11 a-11 c (collectively “FIG. 11”) are perspective views showing a further alternative embodiment of the invention.

FIG. 1 of the drawings shows a robotic, or autonomous, floor cleaning machine in the form of a robotic vacuum cleaner 10. FIG. 2 shows the electrical systems incorporated into the vacuum cleaner 10.

The machine comprises a main body or supporting chassis 12, two driven wheels 15, a cleaner head 40, a user interface with buttons 60 and indicator lamps 65 and various sensors 20-26, 30 for sensing the presence of objects around the machine. Also mounted on the chassis 12 is apparatus 14 for separating dirt, dust and debris from an incoming airflow and for collecting the separated material, a reel for storing a length of power cable 95, and a system for dispensing and rewinding the power cable. The machine 10 is supported on the two driven wheels 15 and a castor wheel (not shown) at the rear of the machine. The driven wheels 15 are arranged at either end of a diameter of the chassis 12, the diameter lying perpendicular to the longitudinal axis of the cleaner 10. The driven wheels 15 are mounted independently of one another via support bearings (not shown) and each driven wheel 15 is connected directly to a traction motor 16 which is capable of driving the respective wheel 15 in either a forward direction or a reverse direction. A full range of manoeuvres is possible by independently controlling each of the traction motors 16.

Mounted on the underside of the chassis 12 is a cleaner head 40 which includes a suction opening facing the surface on which the cleaner 10 is supported. A brush bar 45 is rotatably mounted in the suction opening and a motor 48 is mounted on the cleaner head 40 for driving the brush bar 45. It will be appreciated that the brush bar 45 could be omitted, if desired, so that the cleaner head 40 only has a suction opening and cleans by relying on suction alone. For other types of surface treating machine, the cleaner head 40 could be replaced by a polishing pad, wax dispenser, squeegee etc.

The chassis 12 of the machine 10 carries a plurality of sensors 20-26, 30 which are positioned on the chassis 12 such that the navigation system of the machine can sense obstacles in the path of the machine 10 and also the proximity of the machine to a wall or other boundary such as a piece of furniture. The sensors shown here comprise several ultrasonic sensors 20-26 which are capable of sensing the distance and angular position of walls and objects from the sensors, and several passive infra red (PIR) sensors 30 which can sense the presence of humans, animals and heat sources such as a fire. There are forward-facing sensors 22, 23, side-facing sensors 20, 21 and 24, 25, rear-facing sensors (not shown) and high-level sensors 26. It will be appreciated that the number of sensors, type of sensors and positioning of the sensors on the machine 10 can take many different forms. For example, infra red range-finding devices, also known as PSDs, may be used instead of, or in addition to, the ultrasonic sensors 20-26. In an alternative embodiment the machine may navigate by mechanically sensing the boundary of the working area and boundaries of obstacles placed within the area. One example of a mechanical sensor which could be used on a machine of this type is a “bump” sensor which detects movement of a moveable or resilient bumper when the machine encounters an obstacle. “Bump” sensors can be used in combination with the ultrasonic and PIR sensors described above.

One or both sides of the vehicle can also have an odometry wheel 18. This is a non-driven wheel which rotates as the machine moves along a surface. Each odometry wheel 18 has an encoder associated with it for monitoring the rotation of the odometry wheel 18. By examining the information received from each odometry wheel 18, the navigation system can determine both the distance travelled by the machine and any change in angular direction of the machine. It is preferred that the odometry wheel 18 is a non-driven wheel as this increases the accuracy of the information obtained from the wheel. However, in a simpler embodiment, the machine can derive odometry information directly from the driven wheels 15, by an encoder located on the wheel 15 or the motor 16 which drives the wheel 15.

The machine 10 also includes a motor 52 and fan 50 unit supported on the chassis 12 for drawing dirty air into the machine via the suction opening in the cleaner head 40.

The electrical systems for the machine, shown in detail in FIG. 2, will now be described. The navigation system comprises a microprocessor 80 which operates according to control software which is stored on a non-volatile memory 82, such as a ROM or FLASH ROM. Another memory 84 is used during normal operation of the machine to store data, such as odometry information and a map of the working area (if required), and other operating parameters. The navigation system receives inputs about the environment surrounding the machine from the sensor array 20-26, 30 (including ultrasonic, PIR and bump sensors) and inputs about movement of the machine from odometry wheel movement sensors 18. The navigation system also receives inputs from switches 60 on the user interface, such as starting, pause, stop or a selection of operating speed or standard of required cleanliness. The navigation system provides a plurality of output control signals including signals for driving the traction motors 16 of the wheels 15, a signal for operating the suction motor 52 which drives the suction fan 50 and a signal for operating the motor 48 which drives the brush bar 45. It also provides outputs from illuminating indicator lamps 65 on the user interface. Power is derived from a mains supply via a power cable. The cleaner carries a cable reel 95 with a length of cable (e.g. 20 m) which is sufficient to allow the machine to circumnavigate a typical room in which the machine will be used.

There are various ways of managing cable storage on the machine. FIG. 3 shows one preferred scheme. Power cable 95 is stored on a cable reel 71. The cable reel 71 is permanently biased, by a spring, towards the wound up state. Cable 95 is drawn from the reel 71 by a pair of pinch rollers 70, one of which is driven by a motor 72, under the control of the navigation system, to dispense cable from the reel 71, or to allow cable 95 to be rewound onto the reel 71, as the machine moves around a working area.

In accordance with the invention, means are provided to indicate the orientation of the cable with respect to the chassis. After passing through the pinch rollers 70, the cable 95 passes through an opening 75 in the free end of a pivotable member in the form of a pendulum 74. The pendulum 74 is pivotable about a shaft 73, the pendulum 74 being movable in a vertical plane. Shaft 73 forms part of a rotary encoding device 76, such as a potentiometer, which can provide an output signal proportional to movement of the pendulum 74.

As shown in FIGS. 3B to 3D, the pendulum 74 tracks the position of the cable 95 with respect to the cable reel 71. When the cable 95 is under tension and is pulled out directly behind the machine, the pendulum 74 will be approximately at the central position of FIG. 3B. Thus the potentiometer signal will be small. In FIG. 3C, the cable is to the left of the machine. Thus, the pendulum 74 swings clockwise and the potentiometer 76 provides an output signal indicative of the direction and angle of the cable 95 with respect to the chassis. This is particularly useful when the machine is reversing along a path where cable 95 has been laid. The control system can detect the position of the cable, and the machine can be controlled to follow the path of the cable 95. This technique will hereafter be referred to as ‘cable follow mode’.

In the situation shown in FIG. 3D, the cable is pulled out to the extreme right, and so the pendulum 74 swings anti-clockwise to the position shown. Depending on the sensitivity of the potentiometer, this extreme may be outside the range of angular positions detectable. Thus, a further detector may be provided to detect such extremes. This may take the form of a so-called bump sensor or pressure switch, such as a microswitch. In such a sensor, a signal is output when a resilient part of the sensor is caused to move. Thus, the machine may be arranged with two microswitches on the chassis, either side of the cable. When the cable is to the extreme left or right, it is urged against the resilient part of one of the microswitches, which therefore produces a signal indicative of the extreme position of the cable.

The operation of the machine will now be described with reference to FIGS. 4 to 9. FIG. 4 is a flow chart of the general process for navigating the machine around a working area.

FIGS. 5 to 9 show the machine 10 at work, in a room of a house. The boundary of the working area for the machine is defined by the walls of the room 301-304 and the edges of objects 305-308 placed within the room, such as articles of furniture (e.g. sofa, table, chair). These figures also show the set of paths 320 traversed by the machine.

The machine 10 is placed in the room by a user. Ideally, the machine is left near to a power socket 310 in the room, with the plug inserted into the socket 310 and a short length of power cable lying on the floor between the socket and the machine 10. Once the machine has been switched on, it begins a short routine to discover a starting or ‘home’ position in the room (step 110). The power socket 310 is a convenient home position for the mains powered machine. The ‘home’ position serves as a useful reference point for determining, inter alia, when the machine has travelled around the entire room. The machine determines the position of the power socket 310 by winding the cable 95 onto its internal cable reel 71 as it reverses. The machine can find the socket 310 by mechanically sensing that the cable 95 has been fully rewound, or by detecting a marker 98 placed on the cable 95, near to the plug. The machine then aligns its left hand side with the boundary of the area and starts the suction motor 52 and brush bar motor 48. It waits until the motors 48, 52 reach operating speed and then moves off. As the cleaner moves forwards (step 115) it dispenses power cable 95 from the cable reel so that the cable lies substantially along the path taken by the machine 10. Due to the potential for odometry errors, the cable 95 may be dispensed at a rate which is slightly higher than the rate of movement of the machine 10.

The machine then begins a series of manoeuvres. The series of manoeuvres may comprise, for example, random movements, a spiral pattern, a so-called ‘spike’ pattern, or any combination of movement types. which in combination will be referred to as a ‘spike’. The basic spike is shown in FIG. 7. The machine turns so that it is pointing away from the boundary (wall), inwards into the working area. It travels forwards on a path which is substantially perpendicular to the boundary (step 120). The machine derives information on the distance and direction of travel from the odometry wheel sensors 18. As the cleaner moves forwards, along path 331, it dispenses sufficient power cable 95 from the cable reel 71 so that the cable 95 lies slackly along path 331. During this movement, the machine continually monitors inputs from the sensor array 20-26,30 to sense the presence of any obstacles in its path. The machine continues to travel forwards until one of a number of conditions are met. Should the machine sense the presence of an obstacle (step 125) or the absence of a surface (e.g. a staircase), or if the machine senses that it has dispensed all of the power cable 95 from the reel 71, or if it senses some other fault condition, it will immediately stop. If none of these conditions are met, the machine will stop after a predetermined distance has been travelled from the boundary. This distance will depend on the type of working area where the vehicle is working. In a domestic environment we have found that a maximum distance of 2-3 m works well.

Once the machine has stopped, having met one or more of the conditions mentioned above, it reverses back towards the boundary following a similar path 332 (step 135, FIG. 4). The machine rewinds cable 95 during this return manoeuvre. For best cleaning performance, the suction motor 52 and brush bar motor 48 are operated during this return manoeuvre so as to treat the same area of floor twice. This replicates the kind of ‘to and fro’ cleaning action that a human user performs when they use a vacuum cleaner. As an alternative, during this return manoeuvre the suction motor 52 and brush bar motor 48 can be switched off. This would be a useful way of increasing battery life for a battery powered machine.

During the return manoeuvre, the machine can navigate towards the boundary by using odometry information or it can follow the cable 95 which was laid on the floor during the outward trip, the process previously described as ‘cable follow mode’. Thus, the machine detects the orientation of the cable with respect to the chassis and follows the cable accordingly. This outward trip into the working area and back again to the boundary constitutes the previously mentioned ‘spike’.

As the length of the outward part of the spike increases, the likelihood that the machine will drift from the intended path also increases. Odometry errors, wheel slippage, changes of surface material and the direction of carpet pile are some factors which can cause the machine to drift from an intended path. In the unlikely event that the outward and return paths of the spike are spaced apart and an object lies between the paths, then there is a risk that the power cable can become wrapped around the object. In these circumstances, it is preferable for the machine to navigate back to the boundary in the cable follow mode (steps 137, 138).

Once the machine has returned to the boundary, which it can sense from its sensor array and odometry information, it turns so that it is once again pointing in a clockwise direction, with its left-hand side aligned with the boundary. It moves forwards for a short distance which is sufficient to bring the machine next to the strip of the floor which has just been treated. The cleaner then turns so that it is again pointing away from the boundary, inwards into the working area. The machine then travels forwards at an angle which is substantially perpendicular to the boundary, as before. The machine continues as previously described, traversing a strip of the floor surface which is adjacent, or overlaps, the area previously treated.

The machine repeats this sequence of steps so as to traverse a plurality of paths extending into the working area from the boundary, as can be seen in FIGS. 5 and 6. As the machine progresses around the boundary it can be seen that the spikes originating at different parts of the boundary can overlap one another. This helps to ensure that as much of the working area as possible is treated by the machine 10.

After completing each spike, the machine checks whether it has covered the entire working area (step 140). This check can be performed in various ways. In its simplest form, the machine can use an on-board sensor to sense whether it has returned to a starting position on the boundary. Preferably, a marker 98 is provided on the power cable 95 at a position adjacent the plug so that the machine can sense when it has returned to this position. The marker 98 can be a magnetic marker and the machine can be provided with a magnetic field sensor, such as a Hall-Effect sensor, for sensing the marker. Alternatively, the machine generates a map of the working area and updates this map so as to record areas of floor visited by the machine. Thus, by using this map, the machine can determine when it has completely covered the working area. After each spike the machine also checks (step 145) to ensure that it has sufficient cable 95 remaining on the cable reel 71 to continue travelling around the boundary.

Step 145 requires the machine to have the capability to detect the amount of cable 95 remaining on the cable reel 71. This can be achieved by marking the cable 95 in a manner which indicates the quantity of remaining cable 95 and providing the control system with a sensor which can detect the markings. Alternatively, an encoder on the pinch roller 70 can feed the control system with an indication of the amount of cable 95 dispensed from the reel 71. This is advantageous because the same mechanism can be used to detect any jamming of the cable 95. In a simpler machine this step can be omitted entirely and the machine can simply stop when all of the cable 95 has been dispensed from the reel 71, wherever this may be in the room.

If the machine determines that it has completely covered the working area, it travels back to the starting position in the working area. The machine can follow the boundary of the working area, rewinding the cable 95 as it moves around the boundary. Alternatively, the machine can operate in cable follow mode, rewinding the cable 95 and following the path formed by the cable 95 on the surface of the working area. In the event that this brings the machine near to an obstacle, the machine can revert to a boundary following mode of operation until it is determined that the cable 95 leads away from the obstacle, whereupon the machine can once again operate in cable follow mode. The machine will eventually return to the starting point near to the power socket 310.

In large working areas the machine may run out of cable before it has completely covered the working area. In this case, the machine proceeds to perform the same technique as has previously been described in the opposite direction from the starting point (step 170, FIG. 4). Thus, the cleaner follows the boundary in an anti-clockwise direction, aligning the right-hand side of the machine with the boundary of the area and performing a series of spikes outwardly from the boundary of the working area. FIG. 8 shows the same area as previously shown in FIG. 5. It is assumed that during the initial clockwise trip around the area, the cable was fully dispensed at point X. The machine has returned to the start point at the socket 310 and has begun travelling anti-clockwise around the boundary. The machine begins ‘spiking’ as soon as it returns to the start position. It will be appreciated that the spike movements performed by the machine as it travels anti-clockwise around the boundary are mirror images of the spike movements illustrated in FIG. 7. The machine will continue in this manner until either the cable 95 is again fully dispensed or the navigation system detects that point X has been reached or passed.

FIG. 9 shows an alternative scheme in which the machine, once it has returned to the start point at the socket 310, begins to travel around the boundary in the anti-clockwise direction. However, instead of immediately beginning to spike into the area, it simply travels around the boundary, dispensing cable, until the navigation system detects that point X has been reached or passed. The reason for this difference is because it may be easier for the machine to detect when it reaches point X if the machine travels there directly as there will then be fewer accumulated odometry errors.

For the machine accurately to detect when it has returned to a point where cleaning finished previously (such as point X), it requires some form of mapping function. The machine needs to have the capability to map the working area and record where it has visited in the working area. The map can be constructed using odometry information which is acquired from the odometry wheels 18 and/or information about features of the working area which is acquired from the object detection sensors 20-26, 30 in a manner which is known in the art. The machine can then use the map to determine when it has returned to a point on the boundary which it previously reached via a journey in the opposite direction around the boundary. It is preferable to allow a good overlap region, as accumulated odometry errors can cause some error between the actual position of the machine, and the position of the machine as determined by the map.

If the machine lacks any form of mapping function, then it can simply continue to work in the opposite direction around the working area until the cable has all been dispensed. This can result in a considerable region where the surface is treated twice.

Alternative embodiments of the invention are shown in FIGS. 10 and 11. In FIG. 10, the cable orientation detection mean comprises a pivotable member 77 in communication with a potentiometer 76, as before. However, in this embodiment, the pivotable member 77 is arranged to pivot about a vertical axis 78. The end portions of the member are co-incident with the axis 78, with the central portion of the pivotable member protruding in a horizontal direction. The central portion of the member has an aperture 79, through which the cable 95 extends. Deviations of the position of the cable 95 from the straight back position of FIG. 10 b causes the member 77 to pivot about the axis 78 (FIG. 10 c), which motion is translated into an electrical signal by the potentiometer 76. The signal is proportional to the extent of deflection of the cable 95. This arrangement is suitable for detecting slight deflections. A second cable detector for detecting greater cable deflections is provided in the form of a collar 80 around the cable 95. The collar 80 is pivotable about a vertical axis and is arranged adjacent two microswitches 81, 82, one either side of the collar. As shown in FIG. 10 d, when the cable 95 is deflected to the extreme left with respect to the chassis, the cable pushes against the collar 80 and urges it against the left-hand microswitch 81. Thus, a signal is sent to the control system of the machine indicating that the cable 95 is at an extreme position. Similarly, if the cable 95 extends to the extreme right, the collar 80 depresses the other microswitch 82.

A further alternative is shown in FIG. 11. This embodiment employs a pivotable member 83, also pivotable about a vertical axis 84. The top end portion of the member is in direct communication with a potentiometer 76, also aligned on the vertical axis 84. The central portion of the pivotable member 83 protrudes further in a horizontal direction than does the member of FIG. 10. An aperture 85 is provided for the cable 95. In this embodiment, the pivotable member 83 translates deflection of the cable 95 into rotational motion. This rotation causes the potentiometer 76 to output a signal in dependence on the amount and direction of deflection of the cable 95. It has been found that this embodiment provides satisfactory results for all deflections of the cable, even at extremes. Thus, microswitches are not required in this arrangement.

Further variations may be made without departing from the scope of the invention. For example, the machine need not employ a cable-follow operation. Alternatively, or additionally, the machine may employ signals from the rotary encoder and/or pressure switches in order to avoid running over its own cable or somehow getting tangled in the cable. 

1. An autonomous machine comprising a main body, a power cable and a device for detecting the orientation of the cable with respect to the main body.
 2. An autonomous machine as claimed in claim 1, wherein the device for detecting cable orientation comprises a first detecting device arranged to detect the orientation of the cable within a first predetermined range.
 3. An autonomous machine as claimed in claim 2, wherein the device for detecting cable orientation further comprises a second detecting means device arranged to detect the orientation of the cable within a second predetermined range.
 4. An autonomous machine as claimed in claim 2 or 3, wherein the first detecting device comprises a pivotable member associated with a rotary encoder.
 5. An autonomous machine as claimed in 4, in which the pivotable member comprises a pendulum, one end portion of which is associated with the cable, the other end portion of which is associated with the rotary encoder.
 6. An autonomous machine as claimed in claim 4, wherein the rotary encoder comprises a potentiometer.
 7. An autonomous machine as claimed in claim 3, wherein the second detecting means device comprises a pressure switch arranged to produce a signal when the cable pushes against it.
 8. An autonomous machine as claimed in claim 3, wherein the second detecting means device comprises two pressure switches located on respective sides with respect to the cable, each switch being arranged to produce a signal when the cable pushes against it.
 9. An autonomous machine as claimed in claim 7 or 8, wherein the cable is arranged to push against the or each switch via an intermediary member.
 10. An autonomous machine as claimed in claim 7 or 8, wherein the pressure switch comprises a microswitch.
 11. A vacuum cleaner comprising the autonomous machine of claim 1, 2, 3, 7 or
 8. 12. (canceled)
 13. A method of operating an autonomous machine comprising a main body and a power cable, comprising detecting the orientation of the cable with respect to the main body.
 14. A method as claimed in claim 13, further comprising controlling the machine to follow its own cable.
 15. A method as claimed in claim 14, further comprising causing the machine to collect the cable as it follows it.
 16. A method as claimed in claim 15, in which the causing of the machine to collect its cable comprises causing the cable to be wound on a cable reel carried by the main body.
 17. (canceled)
 18. An autonomous machine as claimed in claim 5, wherein the rotary encoder comprises a potentiometer.
 19. An autonomous machine as claimed in claim 9, wherein the pressure switch comprises a microswitch.
 20. A vacuum cleaner comprising the autonomous machine of claim
 4. 21. A vacuum cleaner comprising the autonomous machine of claim
 5. 22. A vacuum cleaner comprising the autonomous machine of claim
 6. 23. A vacuum cleaner comprising the autonomous machine of claim
 9. 24. A vacuum cleaner comprising the autonomous machine of claim
 10. 